This chapter presents some of the main empirical methods used by economists who since the 1970s have contributed to the elaboration of language policies. This specific focus is the result of the theme of this book; it is more restrictive than discussions on the economics of language of the economics of language policy evaluation. Furthermore, this leads us to emphasize practice-oriented research using quantitative data, in which economists have addressed questions such as: "How much does it cost to make a unilingual education system bilingual?" or "Do actors really benefit from having second-language skills, and if so, how much?" We thus do not discuss epistemological issues, nor do we debate the role of economists in this process.